In a long term evolution (LTE) system, a physical downlink control channel (PDCCH) and a physical downlink shared channel (PDSCH) adopt a time division multiplexing manner in a subframe. An enhanced physical downlink control channel (EPDCCH) is introduced in LTE Rel-11. Different from the PDCCH, a time frequency resource that transmits the EPDCCH in a subframe is in a data area, and the EPDCCH and the PDSCH adopt a frequency division multiplexing (FDM) manner.
When the EPDCCH is transmitted on a physical resource block (PRB) or a PRB pair of a subframe, some positions therein might be used to transmit a reference signal (RS), such as a cell-specific reference signal (CRS), a demodulation reference signal (DMRS), or a channel state information reference signal (CSI-RS). Therefore, it is required to consider that a resource element (RE) corresponding to the RS in a resource area allocated to the EPDCCH cannot be used for EPDCCH transmission, a corresponding encoded output bit needs to adapt a resource available after the RE corresponding to the RS is removed, and meanwhile, the encoded output after modulation is not mapped on the RE, but on a resource other than the RE. Such an adaptation process is called EPDCCH downlink control information (DCI) rate matching and/or EPDCCH resource mapping. In other words, corresponding adaptation and mapping should be performed on the encoded output bit (after modulation) according to a bit (which is modulated as a symbol) that can be borne by a resource corresponding to the encoded output bit and a corresponding resource position. In contrast to the rate matching, when a CRS or a CSI-RS is transmitted on a resource allocated to the EPDCCH, the encoded output does not change correspondingly, and puncturing (puncturing) is performed on a symbol of the EPDCCH on a corresponding RE during resource mapping.
A coordinated multi-point (COMP) transmission technology is introduced in LTE Rel-11, where a main technology therein is a dynamic point selection (DPS) technology. For example, in a heterogeneous network (HetNet), a micro base station is deployed in a hotspot area in coverage of a macro base station, and the macro base station and the micro base station have the same or different cell identifiers (cell ID). A user equipment (UE) at the edge of the micro base station may dynamically select, according to channel quality, a network node between the macro base station and a neighboring micro base station for transmitting data or control signaling. A candidate network node that can be dynamically selected by a UE to transmit data or control signaling is called a DPS network node, which may include network nodes of a limited number, for example, three network nodes. These network nodes may have the same or different cell IDs.
The following scenario is considered: A size of a CoMP measurement set is 3; the CoMP measurement set includes one macro base station and two micro base stations which have different cell IDs: cell ID n, cell ID n+1, and cell ID n+2; and, offsets of CRSs corresponding to the three base stations sequentially differ by one subcarrier in a frequency domain. In the prior art, a UE at the edge of a micro base station does not dynamically select a node for receiving an EPDCCH, but receives the EPDCCH from a base station (for example, a macro base station) of a serving cell of the UE all the time. Correspondingly, corresponding EPDCCH DCI rate matching and/or EPDCCH resource mapping is performed only on an RS of the macro base station, or corresponding resource mapping is performed only on the RS of the macro base station, where puncturing is performed when the EPDCCH is transmitted on the position. Therefore, by adopting the prior art, a network node cannot be flexibly selected for EPDCCH transmission.